The entire disclosures of Japanese Patent Application Nos. 2000-360799 and 2000-360800 filed on Nov. 28, 2000, including specifications, claims, drawings and summaries are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a steam cooling apparatus for a gas turbine. More particularly, the invention relates to cooling apparatus and methods of use.
2. Discussion of the Background
From the viewpoints of economy and effective use of energy resources, various measures for improving efficiency have been implemented in power generation facilities (power generation plants). One of the measures is the employment of a turbine power generation plant (a combined cycle power generation plant) in which a gas turbine and a steam turbine are combined. In the combined cycle power generation plant, high-temperature exhaust gas from the gas turbine is fed to the waste heat recovery boiler, in which steam is generated via a superheating unit, and the thus-generated steam is fed to the steam turbine, in which the generated steam performs work.
A high-temperature component, such as a combustor, of a gas turbine has been cooled with air. However, in order to cope with a recent increase in combustion temperature, cooling with steam has come into use. In relation to a combined cycle power generation plant as well, there is a plan to use a steam turbine in combination with a gas turbine in which a high-temperature component, such as a combustor, is cooled by steam, to thereby obtain a highly efficient power generation plant. For example, steam from a waste heat recovery boiler (intermediate-pressure steam) is bypassed to a combustor, and cooling steam is guided to the combustor, with the amount of the cooling steam being adjusted based on the temperature, pressure, etc. to supply a desired amount of cooling steam to the combustor. Steam after cooling is recovered to the steam turbine side. This configuration results in a combined cycle power generation plant in which a highly efficient cooling system has been constructed.
The present inventors realized that with a conventional steam cooling apparatus for a gas turbine, the amount of cooling steam to be supplied to the combustor is adjusted to feed a desired amount of cooling steam. Thus, the amount of cooling steam can be controlled to a preset flow rate. However, techniques capable of feeding the desired amount of steam to the combustor by a simple configuration have not been established. Furthermore, if the outlet temperature of the combustor is elevated because of any abnormality even when the amount of cooling steam is as set (i.e., if cooling does not take place as planned), the combustor is protected by an interlock function such as trip or runback. Thus, in the event of an increase in the outlet temperature of the combustor due to any abnormality, the efficiency of the entire plant lowers.
The present invention has been accomplished in view of the foregoing circumstances. An object of the present invention is to provide a steam cooling apparatus for a gas turbine which can supply a desired amount of cooling steam to a high-temperature component of the gas turbine, without installing a valve device, which directly adjusts the amount of steam, in an introduction system for cooling steam from a waste heat recovery boiler.
In order to achieve the above object, the present invention provides a steam cooling apparatus for a gas turbine, comprising: a waste heat recovery boiler for generating steam by use of exhaust gas of the gas turbine; a steam turbine operated by means of steam generated by the waste heat recovery boiler; a steam introduction passage for introducing steam from the waste heat recovery boiler into the steam turbine, a steam cooling passage provided in the steam introduction passage and adapted to bypass steam from the waste heat recovery boiler for cooling of a high-temperature component of the gas turbine; generated steam pressure detection means for detecting a pressure of steam generated by the waste heat recovery boiler; a generated steam pressure control valve for controlling a flow rate of steam in the steam introduction passage based on detection information from the generated steam pressure detection means in order to adjust the pressure of steam generated by the waste heat recovery boiler; post-cooling steam temperature detection means provided in the steam cooling passage on a downstream side of the high-temperature component and adapted to detect a temperature of steam after cooling the high-temperature component; and control means which performs open/close control of the generated steam pressure control valve so that a detection value of the generated steam pressure detection means becomes a set value in order to adjust a flow rate of steam flowing into the steam cooling passage based on a state of the gas turbine, and which performs open/close control of the generated steam pressure control valve in order to adjust the flow rate of steam flowing into the steam cooling passage based on detection information from the post-cooling steam temperature detection means.
According to this feature, the flow rate of steam guided into the high-temperature component can be properly controlled by control of the generated steam pressure control valve for maintaining in a predetermined state the pressure of steam generated by the waste heat recovery boiler, without the need to provide the steam cooling passage with an expensive valve device. Moreover, if the steam temperature after cooling rises, control for increasing the flow rate of steam guided into the high-temperature component is performed, making protection of the high-temperature component possible. As a result, an increase in the construction cost of the combined cycle power generation plant call be suppressed, and damage to the high-temperature component, and so forth can be prevented.
The steam cooling passage may branch off from the steam introduction passage ranging from an intermediate-pressure drum to an intermediate-pressure steam turbine: an intermediate-pressure drum pressure control valve may be provided in the steam introduction passage on a downstream side of a branching portion of the steam cooling passage to serve as the generated steam pressure control valve; and the control means may have a function of performing open/close control of the intermediate-pressure drum pressure control valve so as to secure the flow rate in the steam cooling passage by restricting the flow rate in the steam introduction passage based on the detection information from the post-cooling steam temperature detection means.
According to this feature, steam from the intermediate-pressure drum may be fed to the steam cooling passage.
An auxiliary steam introduction passage into which steam from a high-pressure drum is introduced may be connected to the steam cooling passage; an auxiliary steam pressure control valve may be provided in the auxiliary steam introduction passage to serve as the generated steam pressure control valve; and the control means may have a function of performing open/close control of the auxiliary steam pressure control valve so as to secure the flow rate in the steam cooling passage by controlling the flow rate in the auxiliary steam introduction passage based on the detection information from the post-cooling steam temperature detection means.
According to this feature, steam from the high-pressure drum may be fed to the steam cooling.
An auxiliary steam introduction passage into which steam from a high-pressure drum is introduced may be connected to the steam cooling passage; an auxiliary fluid channel may be connected to the auxiliary steam introduction passage; auxiliary steam temperature detection means for detecting a temperature of auxiliary steam may be provided in the auxiliary steam introduction passage on a downstream side of a merging portion of the auxiliary steam introduction passage; an auxiliary fluid pressure control valve may be provided in the auxiliary fluid channel to serve as the generated steam pressure control valve; and the control means may have a function of performing open/close control of the auxiliary steam pressure control valve so as to secure the flow rate in the steam cooling passage by controlling the flow rate in the auxiliary fluid channel based on the detection information from the post-cooling steam temperature detection means and detection information from the auxiliary steam temperature detection means.
According to this feature, steam from the high-pressure drum and auxiliary steam may be fed to the steam cooling passage.
The steam cooling passage may branch off from the steam introduction passage ranging from an intermediate-pressure drum to an intermediate-pressure steam turbine; an auxiliary steam introduction passage into which steam from a high-pressure drum is introduced may be connected to the steam cooling passage: an intermediate-pressure drum pressure control valve may be provided in the steam introduction passage on a downstream side of a branching portion of the steam cooling passage to serve as the generated steam pressure control valve; an auxiliary steam pressure control valve may be provided in the auxiliary steam introduction passage to serve as the generated steam pressure control valve; and the control means may have functions of performing open/close control of the intermediate-pressure drum pressure control valve so as to secure the flow rate in the steam cooling passage by restricting the flow rate in the steam introduction passage based on the detection information from the post-cooling steam temperature detection means, and performing open/close control of the auxiliary steam pressure control valve so as to secure the flow rate in the steam cooling passage by controlling the flow rate in the auxiliary steam introduction passage based on the detection information from the post-cooling steam temperature detection means.
According to this feature, steam from the intermediate-pressure drum, and steam from the high-pressure drum and auxiliary steam may be fed to the steam cooling passage.
The present invention has also been accomplished in view of the above circumstances. Another object of the present invention is to provide a steam cooling apparatus for a gas turbine which can protect a high-temperature component, without using an interlock function, even if the temperature on the outlet side of the high-temperature component increases.
In order to achieve the above object, the present invention provides a steam cooling apparatus for a gas turbine, comprising; a waste heat recovery boiler for generating steam by use of exhaust gas of the gas turbine; a steam turbine operated by means of steam generated by the waste heat recovery boiler: a steam introduction passage for introducing steam from the waste heat recovery boiler into the steam turbine; a steam cooling passage provided in the steam introduction passage and adapted to bypass steam from the waste heat recovery boiler for cooling of a high-temperature component of the gas turbine; a steam amount control valve provided in the steam cooling passage and adapted to control an amount of steam introduced into the steam cooling passage; post-cooling steam temperature detection means provided In the steam cooling passage on a downstream side of the high-temperature component and adapted to detect a temperature of steam after cooling the high-temperature component; and control means which performs open/close control of the steam amount control valve in order to adjust a flow rate of steam flowing into the steam cooling passage based on detection information from the post-cooling steam temperature detection means, and which controls the flow rate of steam flowing into the steam cooling passage to a predetermined state.
According to this feature, if the steam temperature after cooling rises, the steam amount control valve is controlled so as to increase the flow rate of steam guided into the high-temperature component. As a result, the amount of cooling steam is increased to make protection of the high-temperature component possible. Consequently, the high-temperature component can be protected, without using an interlock function, even if the temperature on the outlet side of the high-temperature component increases. Thus, damage to the high-temperature component, and so forth can be prevented.
The steam cooling apparatus for a gas turbine according to the present invention also comprises: a waste heat recovery boiler for generating steam by use of exhaust gas of the gas turbine; a steam turbine operated by means of steam generated by the waste heat recovery boiler; a steam introduction passage for introducing steam from the waste heat recovery boiler into the steam turbine; a steam cooling passage provided in the steam introduction passage and adapted to bypass steam from the waste heat recovery boiler for cooling of a high-temperature component of the gas turbine; generated steam pressure detection means for detecting a pressure of steam generated by the waste beat recovery boiler; a generated steam pressure control valve for controlling a flow rate of steam in the steam introduction passage based on detection information from the generated steam pressure detection means in order to adjust the pressure of steam generated by the waste heat recovery boilers a steam amount control valve provided in the steam cooling passage and adapted to control an amount of steam introduced into the steam cooling passage, post-cooling steam temperature detection means provided in the steam cooling passage on a downstream side of the high-temperature component and adapted to detect a temperature of steam after cooling the high-temperature component: and control means which performs open/close control of the generated steam pressure control valve so that a detection value of the generated steam pressure detection means becomes a set value in order to adjust a flow rate of steam flowing into the steam cooling passage based on a state of the gas turbine, and which performs open/close control of the generated steam pressure control valve and the steam amount control valve in order to adjust the flow rate of steam flowing into the steam cooling passage based on detection information from the post-cooling steam temperature detection means.
According to this feature, if the steam temperature after cooling rises, the generated steam pressure control valve and the steam amount control valve are controlled so as to increase the flow rate of steam guided into the high-temperature component. As a result, the amount of cooling steam is increased to make protection of the high-temperature component possible. Consequently, the high-temperature component can be protected, without using an interlock function even if the temperature on the outlet side of the high-temperature component increases. Thus, damage to the high-temperature component, and so forth is prevented.
The steam cooling passage may branch off from the steam introduction passage ranging from an intermediate-pressure drum to an intermediate-pressure steam turbine; an intermediate-pressure drum pressure control valve may be provided in the steam introduction passage on a downstream side of a branching portion of the steam cooling passage to serve as the generated steam pressure control valve; and the control means may have a function of performing open/close control of the intermediate-pressure drum pressure control valve so as to secure the flow rate in the steam cooling passage by restricting the flow rate in the steam introduction passage based on the detection information from the post-cooling steam temperature detection means.
According to this feature, steam from the intermediate-pressure drum can be fed to the steam cooling passage.
An auxiliary steam introduction passage into which steam from a high-pressure drum is Introduced may be connected to the steam cooling passage: an auxiliary steam pressure control valve may be provided in the auxiliary steam introduction passage to serve as the generated steam pressure control valve; and the control means may have a function of performing open/close Control of the auxiliary steam pressure control Valve so as to secure the flow rate in the steam cooling passage by controlling the flow rate in the auxiliary steam introduction passage based on the detection information from the post-cooling steam temperature detection means.
According to this feature, steam from the high-pressure drum can be fed to the steam cooling passage.
The steam cooling passage may branch off from the steam introduction passage ranging from an intermediate-pressure drum to an intermediate-pressure steam turbine; an auxiliary steam introduction passage into which steam from a high-pressure drum is introduced may be connected to the steam cooling passage; an intermediate-pressure drum pressure control valve may be provided in the steam introduction passage on a downstream side of a branching portion of the steam, cooling passage to serve as the generated steam pressure control valve; an auxiliary steam pressure control valve may be provided in the auxiliary steam introduction passage to serve as the generated steam pressure control valve; and the control means may have functions of performing open/close control of the intermediate-pressure drum pressure control valve so as to secure the flow rate in the steam cooling passage by restricting the flow rate in the steam introduction passage based on the detection information from the post-cooling steam temperature detection means, and performing open/close control of the auxiliary steam pressure control valve so as to secure the flow rate in the steam cooling passage by controlling the flow rate, in the auxiliary steam introduction passage based on the detection information from the post-cooling steam temperature detection means.
According to this feature, steam from the intermediate-pressure drum, steam from the high-pressure drum and auxiliary steam can be fad to the steam cooling passage.
The control means may also have a function of fully opening the steam amount control valve when the post-cooling steam temperature detection means detects that the steam temperature exceeds an upper limit.
According to this feature, when the steam temperature exceeds the upper limit, the maximum amount of steam can be passed through the steam cooling passage.